Codigestion of food waste and real traditional Chinese medicine wastewater in anaerobic membrane bioreactor: Stability mechanism and microbial community dynamics.

The treatment of real traditional Chinese medicine (TCM) wastewater still poses a major challenge. In this study, the complementary properties of TCM wastewater and food waste (FW) were exploited, and a 230-day long-term experiment using an anaerobic codigestion (AcoD) system coupled with an anaerobic membrane bioreactor was conducted, thereby aiming to systematically analyse the stability mechanism of the AcoD system. The results revealed that the AcoD system could maintain stable operation at a volume ratio of 25% TCM wastewater to 75% FW under a prolonged hydraulic retention time and a reduced organic loading rate, with a methane content of approximately 60% and a chemical oxygen demand removal efficiency exceeding 97%. Increasing the proportion of TCM wastewater to 50% induced irreversible acidification (pH<6.3) and complete system collapse. Efficient organic removal was realized via the combined effect of microbial degradation and membrane interception, whereas the accumulation of extracellular polymeric substances led to membrane fouling. The results of metagenomic analysis demonstrated that enrichment of Thermodesulfobacteriota and Nitrospirota effectively mitigated the biotoxicity of TCM wastewater. Moreover, the presence of TCM-derived antimicrobial substances resulted in an increase in the abundance of tetracycline and macrolide antibiotic resistance genes, exerting selective pressure on microorganisms and inhibiting methanogenic activity. Acetoclastic methanogenesis was identified as the dominant methanogenic pathway, which is accompanied by hydrogenotrophic methanogenesis. Notably, the addition of TCM wastewater induced microbial stress responses, thereby inhibiting biofilm formation on the membrane surface. This study provides a new perspective on membrane fouling control and a theoretical basis for the treatment of real TCM wastewater.